This is rather interesting. Growing up in the UK the only place I could ever find Pepsi was at a KFC. McDonalds and most restaurants all have Coke. My first drink of Pepsi was at my friends' house whose father only ever got fast food from Burger King (which was impossible to find in my area of the UK because they use lower quality beef) so drank Pepsi.

As an adult I've found the only relevant things for colas. Coke goes great with white rums and Pepsi goes great with spice rums. Beyond that I'll drink either whenever.